This invention relates generally to transaxles and, more particularly, relates to a controlled traction cartridge for use in providing a controlled traction differential.
As is known, the use of a standard differential assembly in the transmission system of a motor vehicle allows the wheels to spin at different speeds. In the case of a vehicle traveling in a straight line, the axle shafts connected to the standard differential assembly will rotate at the same speed. However, when a turn or curve is encountered, the axle shaft nearest the inside of the turn will slow in rotational speed while the outer axle shaft will simultaneously increases in rotational speed. As such, the wheels, driven by the axle shafts, are prevented from scuffing the surface across which they travel.
While the standard differential assembly serves an important function in the operation of a transmission system, the standard differential of simple construction has difficult operating under certain conditions. For example, when a first one of the drive tires is disposed in wet, muddy, or loose soil conditions, or when the first drive tire has been partially or completely removed from contact with the ground, the coefficient of friction under the first drive tire will be substantially lower than that associated with the second drive tire. This resulting frictional imbalance will tend to cause the second drive tires to remain stationary while the first drive tire will spin without moving the vehicle.
To solve the problem of loss of traction in larger transaxle systems, a variety of techniques have been developed to reduce the tendency of the transaxle to differential. For example, U.S. Pat. No. 3,528,323 to Kamlukin, issued Sep. 15, 1970, discloses a means for preventing free spinning of one of the driven shafts of a transaxle without interfering with the normal differential capability of the transaxle. In particular, the ""323 patent discloses the use of a coil spring to outwardly force the gears of the differential into engagement with the differential housing thereby introducing a frictional force into the assembly which acts to resist relative rotation of the axle shafts. In this manner, the frictional force limits the free spinning of one axle shaft while the other remains stationary.
While the friction inducing means disclosed in the ""323 patent works for its intended purpose to provide larger transaxles with a controlled traction differential assembly, the use of coil springs to apply the frictional force often requires special tools and/or procedures for use in applying the forces necessary to set the springs. These additional tools and/or procedures undesirably results in increased manufacturing costs. Therefore, there remains a need for a controlled traction differential assembly which is simpler to construct, can be produced at a lower cost, and which can be readily incorporated into a smaller transaxle such as an integrated hydrostatic transaxle.
As a result of these existing needs, it is an object of the present invention to provide an integrated hydrostatic transaxle having a controlled traction differential assembly which will provide the hydrostatic transaxle with the benefits and advantages which have accrued to other types of transaxles that use controlled traction differential assemblies.
It is a further object of the present invention to provide a controlled traction differential assembly which is cost effective and relatively easy to manufacture.
It is still a further object of the present invention to provide a controlled traction cartridge for use in conveniently converting a standard differential assembly into a controlled traction differential assembly.
It is yet a further object of the present invention to provide a controlled traction differential assembly in which the breakdown bias, i.e., the amount of torque required to cause the differential to operate, may be easily varied.
In accordance with these objects, an integrated hydrostatic transaxle is provided. Generally, the transaxle comprises a hydrostatic transmission including a center section on which is supported a hydraulic pump unit and a hydraulic motor unit and a motor shaft drivingly connected to the hydraulic motor unit. A differential assembly is drivingly linked to the motor shaft for use in driving a pair of axle shafts. The differential assembly comprises a pair of gears rotatable with respect to each other and a friction inducing means for use in frictionally inhibiting the movement of at least one of the pair of gears with respect to the other of the pair of gears. In this manner the frictional force applied to the gear prevents normal operation of the differential when the drive tires mounted upon the axle shafts are under conditions of frictional imbalance.
More specifically, the differential assembly includes a pair of gears rotatable with respect to each other which are both disposed between an interior and an exterior bearing surface. The interior and the exterior surfaces are compressed against the pair of gears to maintain the gears in frictional engagement therewith thereby inhibiting the rotational movement of the pair of gears with respect to one another. In a preferred embodiment of the invention, the interior bearing surface is provided by forming at least one shoulder on a cross shaft which supports the pair of gears and the exterior bearing surface is provided by a pair of bearing blocks.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and is indicative of the various ways in which the principles of the invention may be employed.
In accordance with these objects, the invention resides in a controlled traction cartridge for use in connection with a differential. The cartridge generally comprises a shaft, a gear mounted on the shaft and rotatable with respect thereto, and an interior bearing surfaces associated with the shaft. The gear is maintained in frictional engagement with the interior bearing surface for inhibiting the rotation of the gear.
More specifically, the invention resides in a differential and cartridge for use therein which comprises a hollow shaft supporting a pair of interior bearing surfaces, a pair of bearing blocks carried by the shaft, and a pair of gears mounted on the shaft and rotatable with respect to each other. The gears are each disposed in frictional engagement with a corresponding one of the bearing blocks and a corresponding one of the interior bearing surfaces. A nut and bolt assembly is disposed through the shaft and is used to maintain the frictional engagement between the pair of bearing blocks, the pair of gears, and the pair of interior bearing surfaces.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and is indicative of the various ways in which the principles of the invention may be employed.